                                     acc))))))               ;WHOA! :)
 ;my solution is more general though, allowing transforming function not to
 ;return list - this function is heavily "cludged" to accomodate solution to 3.21 and
-;to keep ... "generality"... clap! clap! clap! :)
+;to keep ... "generality"... clap! clap! clap! :) (ironical self-criticsm)
 
 ;fpins - strictly assumes transforming function returns list thus it is simpler
 (defn flat-map-fpins [xs f]

  (flat-map-fpins xs #(if (f %) (list %) nil)))
;-----------------------------------------------------------------------


(ns fpinscala.datastructures
  (:use clojure.test))

(defn append [xs ys]
  (if (nil? xs)
